If $x \triangleleft y = x+5y$ and $x \circledcirc y = 4x-2y$, find $(-3 \circledcirc -4) \triangleleft -6$.
Solution: First, find $-3 \circledcirc -4$ $ -3 \circledcirc -4 = (4)(-3)-(2)(-4)$ $ \hphantom{-3 \circledcirc -4} = -4$ Now, find $-4 \triangleleft -6$ $ -4 \triangleleft -6 = -4+(5)(-6)$ $ \hphantom{-4 \triangleleft -6} = -34$.